Pitot tube



y 1955 w. R. CARPENTER 3,181,356

PITOT TUBE Filed Oct. 24, 1962 I N VE N TOR MM /4M 1?. CAWFE/VTA-V? NZ WUnited States Patent Ofiice 3,181,356 PHTOT TUBE William lit. Carpenter,Muslregon, Mich, assignor to Carpenter Corporation, a corporation ofMichigan Filed st. 24, E962, der. No. 232,747 4 Qlaims. (ill. 73-482)This invention relates to marine instruments and more particularly to aPitot tube type device for actuating a marine speedometer.

Marine speedometers operated by the dynamic pressure created in a closedconduit as a result of having one end of the conduit exposed to thewater in the direction of movement of the boat are well-known. Thisinvention is designed to overcome one of the most commonly experienceddificulties with this type of device. Many boats, and particularlypleasure craft, are operated in waters where there is a greater or alesser amount of marine vegetation floating in the water. This marinevegetation frequency enters the water-receiving opening of the devicepartially or wholly plugging it with the result that the speedometereither ceases to function or gives entirely false readings. Many deviceshave been developed in an effort to overcome this difficulty. Thesedevices have met with little or at best limited success.

This invention provides a solution for this problem by so guarding theopening to the conduit which leads to the speedometer, that the marinevegetation is positively cleared from the water before it can enter theopening. Therefore, the continued accurate operation of the instrumentis assured.

The objects and advantages of this invention will be immediatelyunderstood by those acquainted with marine instruments by reading thefollowing specification and the accompanying drawings.

in the drawings:

PEG. 1 is a side elevation view of the invention;

FIG. 2 is a sectional view taken along the plane ll-Il;

FIG. 3 is a sectional view taken along the plane lll Ill;

FIG. 4 is a sectional view taken along the plane IV A TV; and

H6. 5 is a sectional view taken along the plane VV. l have provided aPitot tube device desgned to be submerged in the water. The device has aleading edge of thin section and a water entry aperture which is guardedby a forwardly extending fin or web. This latter web acts either as asweep to remove weeds from in front of the water entry opening or as aknife to cut the weeds before they become lodged for any substantialperiod of time in front of the opening. it also keeps the vegetation ashort distance ahead of the opening, thus preventing its entry. in thismanner, the opening is kept clear of obstructions.

Referring specifically to the drawings, the numeral it) indicates afragmentary portion of the hull of a boat. To this is secured, by anysuitable means such as screws, a mounting bracket ll which supports thebody element E12; by means of the hinge pin 13. The use of the mountingbracket 11 and the fact that the body element 12 is hingedly secured toit is immaterial to this invention since these facets of theconstruction are conventional and well known.

The body element has a flow stabilization flange Zll. Below the flange2t), the body element projects downwardly at an inclined angle. From theflangeTownwardly, the body element is tapered in cross section. As isshown in FIG. 2, the body element is generally flat on the upper surface21 and has one side face 22 which is generally flat while the other face2-3 is curved in a downward direction to converge with the face 22forming ildlfiiid Patented May 4, 1965 a leading edge 24 which is sharpand thus of narrow cross section. This leading edge is at one side ofthe body element making it possible to develop the hereinafter describedpocket and aperture. The leading edge 24 is sloped back at an angle ofapproximately 45. This inclination causes any weeds which might strikeit to slide downwardly and off the bottom end of the body member. Shouldthe weeds, for any reason, tend to try to remain on the edge, they willslowly be moved down the edge and the sharpness of the leading edge 24will tend to sever them thus releasing them from the body memher. itwill be noted that the body member not only is tapered downwardly andforwardly toward the leading edge 24 but, as is clearly shown in theseveral sections illustrated in FIGS. 2 through 5, the body memher istapered toward its free or lower end.

Adiacent its lower end, the body member has a recessed pocket 25 openingoutwardly through the leading edge. The upper wall 26 of this pocket(FIGS. 1 and 3) extends rearwardly from the leading edge of the bodymember in a generally horizontal plane when the body member is inoperating position as illustrated in FIG. 1. This upper wall 26intersects at a right angle with a forwardly facing rear wall 27. Therear wall 27 thus faces forwardly or in the direction of movement of thedevice through the water.

On one side of the recessed pocket 25, a guard web or fin 2.8 isprovided. The forward edge of this fin is either narrow or may bebrought to a sharp, shearing edge. Like the leading edge 24 of the bodymember, it also is sloped downwardly and rearwardly to either sweepweeds away from the area or cut them, if they become lodged and are notswept olf the end of the body mem ber.

Extending rearwardly from the recessed pocket 25, through the rearwardwall 27 of the pocket, is an aperture 29. This aperture opens throughthe rearward wall 27 at a point upwardly and recessed from the leadingedge of the guard fin 28 as is clearly shown in FIG. 5. Thus, it issituated well within the guarded or protected portion of the pocket. Itwill be noted from FIG. 5 that the aperture 29 is nestled down at thejunction of the inner face of the guard fin 28 and the upper andrearward walls 26 and 27 where it receives maximum protection from thepresence of the fin. The aperture 29 communicates at its rearward endwith a conduit 30 which extends lengthwise of the body member adjacentits upper or rearward edge. The lower end of the conduit 39 is closed byany suitable permanent plug 31 (FIG. 4). The upper end of the conduit 30communicates with a tube 32 which extends to and is connected with thespeedometer with which this invention is operated.

In operation, the device is moved through the water in the direction ofthe arrow A in FIG. 1. Weeds striking the leading edge 24 of the bodymember are, by reason of its inclination, induced to slide downwardlyand be released by passing over the end of the structure. Should theweeds, for any reason, tend to become lodged against the leading edgeand refuse to be released in this manner, the pressure of the Waterpushing them against the sharp leading edge 24 will tend to cut them andthe weeds will be released and be prevented from accumulating. Thus, thedevice will not tend to become a rake or collection device for weeds asit is moved through the water.

The weeds that tend to be collected in the area of the pocket 25 aresimilarly disposed of. The presence of the fin 23 and the angle ofinclination of its leading edge bias the weeds to slide downwardly overthe end of the body member and thus be released. Once again, should theweeds resist this type of movement, the sharpness of the leading edge ofthe fin 28 will tend to shear them so that they will be released in thismanner. The forward projection of the fin keeps the weeds well forwardof the open end of the aperture 2?, preventing any portion of the Weedsfrom entering this opening and tending to plug it. Further, the presenceof the fin tends to push to one side or the other any small lengths ofweeds which may be encountered also guarding this opening and keeping itfrom becoming plugged. In this manner, this invention both prevents theactual opening 29 itself from being plugged by weeds entering it andalso prevents the accumulation of weeds immediately ahead of the openingwhich also will disturb the water flow in this area, tending to lessenthe dynamic pressure which should be read by the instrument. Thus, theinvention contributes materially to the proper functioning of thespeedometer and to the accuracy of the readings when it is operating.The relationship between the size of the orifice 29, the flat surface 26and the shape of the guard fin 28 is important to the effectivefunctioning of the invention. If the upper end of the guard fin iscarried into the leading edge 24 rather than recessed rearwardly fromit, as shown, it materially reduces the accuracy of the readings whichwill be produced. For this reason the upper end of the guard fin 28 isrecessed approximately one-half the fore and aft length of the surface26. If the leading edge of the guard fin is made concave or is radiusedrather than being sharp, this also produces a detrimental effect uponreadings produced by the invention.

The actual manner in which this device operates is conventional so faras its utilization of the principle of utilizing the dynamic pressure ofthe water created by the movement of the device through the water toapply a pressure to the reading instrument which reading instrumentconverts into a measure of speed. Therefore, further explanation of thisfacet of the devices characteristics is not considered necessary.

The bracket 11 and the body member 12 may each be fabricated of anysuitable material, such as a molded plastic or a cast metal, such asaluminum. Certain synthetic resinous plastics have the desirablecharacteristics of a slippery or lubricious surface which would tend toincrease the tendency of Weeds to slide along the body member fordiscard. An example of such a synthetic resinous material would be aNylon. The fact that the extreme lower end of the device beyond therecessed pocket tends to be more conventional or rounded in crosssection as shown in FIG. 4, does not affect the operation of this devicesince any weeds which reach this point have already been moved beyondthe point where they will influence the entrance of water into theaperture 29 and are further so close to the end of the body member, thatthey will be forced from the body member by the pressures exerted by thewater moving past the device. Any weeds which pass in front of therecessed pocket 25 will be moved on rapidly and will result in no morethan a momentary fluctuation in the readings given by the device.

While a preferred embodiment of this invention has been described, itwill be recognized that various modifications of the invention may bemade each without departing from the principle of the invention.

I claim:

1. In a Pitot tube type device for actuating a marine speedometer, abody member, said body member being inclined downwardly and rearwardlyand having a con duit adapted to be connected to the speedometer; saidbody member having a sharp, knifelike leading edge offset to one side ofthe body and inclined similarly to said body member; said body memberhaving a forwardly opening recessed pocket therein adjacent its lowerend;

a Water receiving aperture communicating with said conduit and openinghorizontally and forwardly into said pocket, said pocket having ahorizontal upper wall; a guard fin olfset to the same side of said bodymember as said leading edge and closing one side of said pocket andsituated to one side of said aperture and projecting a substantialdistance ahead of the opening of said aperture into said pocket forsweeping weeds from the water before they can enter said aperture, saidguard fin being recessed rearwardly from said leading edge and saidupper wall extending forwardly of said guard fin to said leading edgewhereby turbulence in the flow pattern of water at said aperture iseliminated.

2. In a Pitot tube type device for actuating a marine speedometer, abody member, said body member being inclined downwardly and rearwardlyand having a conduit adapted to be connected to the speedometer; saidbody member having one side converging toward the other side to form aleading edge of thin section along an offset to one side thereof and arecessed pocket adjacent the lower end thereof; a water receivingaperture communicating with said conduit and opening horizontally intosaid pocket; said pocket having a fiat horizontal upper wall; a guardfin aligned with said leading edge closing one side of said pocket andsituated to one side of said aperture and projecting a substantialdistance ahead of the opening of said aperture into said pocket forsweeping weeds from the water before they can enter said aperture, theforward edge of said guard fin being sharp, inclined at generally thesame angle as said leading edge and forming a straight line; the forwardedge of said guard fin merging into said upper wall at a point offsetrearwardly from said leading edge of said body member and said upperwall projecting forwardly of said guard fin to said leading edge; saidaperture being nested in the apex formed at the juncture between saidupper wall and said guard fin whereby turbulence in the flow pattern ofwater at said aperture is eliminated.

3. A Pitot tube type device as described in claim 2 wherein said angleof inclination is approximately 45.

4. In a Pitot tube type device for actuating a marine speedometer, abody member having a conduit adapted to be connected to the speedometer;said body member having a downwardly and rearwardly inclined narrowleading edge offset to one side thereof; a pocket adjacent the lower endof said leading edge of said body member; a water receiving aperturecommunicating with said conduit and opening horizontally into saidpocket; a guard fin closing one side of said pocket and situated to oneside of said aperture, said olfset being in the same direction as thatof said leading edge, said guard fin projecting a substantial distanceahead of the opening of said aperture into said pocket for sweepingweeds from the water before they can enter said aperture, the forwardedge of said guard fin being a straight line; the forward edge of saidguard fin at its upper end being offset rearwardly of said leading edgeof said body member; said pocket having a flat horizontal upper wallextending from said aperture past said guard fin to said leading edge ofsaid body member and cooperating with said guard fin to guide water instraight flow lines to said aperture.

References Cited by the Examiner UNITED STATES PATENTS 1,099,206 5/14Sanborn 73-182 3,082,623 3/63 Bosland 73-182 3,084,543 4/63 Finkl 73-182ISAAC LISANN, Primary Examiner.

LEONARD F ORMAN, Examiner.

UNITED STATES PA'lE1\T OFFICE CERTIFICATE OF CORRECTION Patent No.3,181,356 May 4, 196

William Rf Carpenter It is hereby certified that error appears in theabove numbered patent reqiiring csrrectio'n and that the said LettersPatent should read as corrected below Column 1, line 44, for desgned"read designed column 4, line 19, for "an" read and Signed and sealedthis 16th day of November 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Aucsting Officer Commissioner ofPatents

1. IN A PITOT TUBE TYPE DEVICE FOR ACTUATING A MARINE SPEEDOMETER, A BODY MEMBER, SAID BODY MEMBER BEING INCLINED DOWNWARDLY AND REARWARDLY AND HAVING A CONDUIT ADAPTED TO BE CONNECTED TO THE SPEEDOMETER; SAID BODY MEMBER HAVING A SHARP, KNIFELIKE LEADING EDGE OFFSET TO ONE SIDE OF THE BODY AND INCLINED SIMILARLY TO SAID BODY MEMBER; SAID BODY MEMBER HAVING A FORWARDLY OPENING RECESSED POCKET THEREIN ADJACENT ITS LOWER END; A WATER RECEIVING APERTURE COMMUNICATING WITH SAID CONDUIT AND OPENING HORIZONTALLY AND FORWARDLY INTO SAID POCKET, SAID POCKET HAVING A HORIZONTAL UPPER WALL; A GUARD FIN OFFSET TO THE SAME SIDE OF SAID BODY MEMBER AS SAID LEADING EDGE AND CLOSING ONE SIDE OF SAID POCKET AND SITUATED TO ONE SIDE OF SAID APERTURE AND PROJECTING A SUBSTANTIAL DISTANCE AHEAD OF THE OPENING OF SAID APERTURE INTO SAID POCKET FOR SWEEPING WEEDS FROM THE WATER BEFORE THEY CAN ENTER SAID APERTURE, SAID GUARD FIN BEING RECESSED REARWARDLY FROM SAID LEADING EDGE AND SAID UPPER WALL EXTENDING FORWARDLY OF SAID GUARD FIN TO SAID LEADING EDGE WHEREBY TURBULENCE IN THE FLOW PATTERN OF WATER AT SAID APERTURE IS ELIMINATED. 